Exemplary embodiments of the present invention relate to a method for manufacturing a fabric type circuit board, and more particularly, to a method for manufacturing a fabric type circuit board forming a circuit pattern so as to operate electronic parts on a fabric material.
Recently, as an interest in a wearable computer has been rapidly increased, flexible input devices, communication devices, or the like, that are installed on a garment have been developed.
In particular, an attempt to use a fabric as a circuit board has been continuously conducted. When the fabric is used as the circuit board, the substrate is made of the same material as a garment, thereby making it possible to minimize foreign materials.
An example of a technology for forming a conductive circuit pattern on a fabric may include a transfer method, a deposition method, a printing method, an embroidery method, or the like.
The deposition method has been used to form a flexible PCB (FPCB) or a flexible copper clad laminate (FCCL) on a film or to manufacture a conductive thread, an EMI shielding fabric, a conductive tape, or the like, by thinly coating a thin film on a thread or a fabric. A simple circuit board may be manufactured by dicing the conductive tape in a circuit pattern shape and sticking the diced conductive tape to a fabric.
The transfer method prints a desired shape with transfer ink and transfers the printed shape to a fabric by thermo compressing the printed shape to the fabric. As an example of the transfer method may include various methods such as a thermal transfer method, a sublimation transfer method, an adhesive transfer method, or the like. The transfer method used for the fabric has been mainly used to decorate a fabric with pictures, logos, characters, or the like.
The printing method is performed by various kinds of printing processes such as a screen printing inkjet printer, a gravure printing inkjet printer, a flexo printing inkjet printer, or the like. In this case, the printing method prints and thermoplasticizes the pattern by commonly using the conductive ink to conduct electricity through the printed pattern.
The embroidery method conducts electricity by backstitching patterns or lines using a conductive thread.
As a relevant prior art, there is Korean Laid-Open Patent No. 10-2010-0084334 (Jul. 26, 2010) entitled “Printed Circuit Board of Fabric Type Using Metal Tape and Metal Thin Paper and Manufacturing Method Thereof”.
As such, the fabric type circuit board may be strong against stress such as various types of external torsions and is more flexible. On the other hand, due to the above-mentioned advantages, it is difficult to form the circuit pattern on the fabric. In particular, the above-mentioned methods have several problems when a line width of about 0.3 mm is implemented.
In the case of the embroidery method, it is difficult to manage a knot of the thread and implement a fine circuit pattern. In the case of the deposition and plating methods, it is difficult to deposit the fine circuit pattern on the fabric like a general film substrate. The plating method cannot also be applied to the fabric.
The printing method can print the fine circuit pattern when the fabric is selected well, but can easily disconnect the pattern due to the external stress like bending.
The transfer method may be used to thinly stack electronic parts. As a relevant study using an electrode pattern used for a fabric, there is a STELLA project that has been researched in Europe.
The STELLA project may use flexible thermal polyurethane (TPU) as a base substrate for forming a circuit pattern to form an electrode pattern by an existing flexible PCB manufacturing method, extend a pattern formed by connecting the electrode pattern in a U-letter shape up and down, and may use the pattern bonded to the base substrate like a fabric by applying heat to the TPU that is the base substrate.
However, the transfer method may hinder ventilation of a fabric by applying the TPU to the whole bonding surface, hardly form the fine circuit pattern due to the flexible base substrate, and degrade adhesion when the transferred fabric does not fit with TPU resin.